Ultrasonic diagnosis apparatuses, which are one type of diagnostic imaging apparatuses, are frequently used for diagnosis, since they are easy to handle and are capable of performing noninvasive observation of arbitrary cross sections in real time. On the other hand, ultrasonic images captured by the ultrasonic diagnosis apparatuses are generally inferior in image quality to tomographic images captured by X-ray CT apparatuses or the like. Thus, comprehensive diagnosis may be performed while performing comparison with a tomographic image captured by another diagnostic imaging apparatus, such as an X-ray CT apparatus or an MRI apparatus (the tomographic image will hereinafter be referred to as a “reference image”). For example, when hepatophyma or the like is treated by radiofrequency ablation under the guidance of an ultrasonic image, it is conceived that a treatment portion is pre-located by CT diagnosis and a CT image thereof is used as a reference image to perform the guidance with the ultrasonic image.
However, when a CT image or MR image is merely rendered as the reference image to recognize an association relationship between the images is a great burden on the operator. This is because the reference image provided by a CT image or MR image is typically a tomographic image of a cross section perpendicular to a body axis, whereas the ultrasonic image is a tomographic image of an arbitrary cross section specified by the operator.
Non-patent Document 1 describes an approach to facilitate the recognition of an association relationship between a reference image and an ultrasonic image. In the approach, a position sensor is attached to an ultrasonic probe to determine an ultrasonic scan plane and a reference image of the same cross section as the ultrasonic scan plane is reconstructed from multi-slice image data (hereinafter referred to as “volume image data”) of a CT image or MR image and is rendered on a display screen. Similarly, Patent Document 1 also proposes a technology in which a reference image of the same cross section as an ultrasonic scan plane is reconstructed from the volume image data of a CT image or MR image and the reference image and an ultrasonic image are rendered on a display screen in an aligned or superimposed manner or in an alternately switched manner.
Patent Document 2 proposes a technology to aid manipulation for introducing a puncture needle into a body. That is, an ultrasonic scan plane is controlled so as to include the puncture needle and a reference image corresponding to the ultrasonic scan plane is cut out and is displayed. In the technology, two markers are attached to a body surface at a position corresponding to a patient's diseased area, into which the puncture needle is to be inserted, to obtain the volume image data of a reference image. Further, an ultrasonic probe is provided with an introducing portion for the puncture needle, so that the position and the angle of the puncture needle relative to the probe is fixed, and a sensor for detecting the position and the angle of the probe is attached to the probe to determine the ultrasonic scan plane. In this manner, a coordinate system for the volume image data and a coordinate system for the ultrasonic scan plane are associated with each other and a reference image corresponding to the ultrasonic scan plane is cut out and is displayed.                Non-patent Document 1: “Radiology” RNSA issued in 1996, page 517, K. Oshio        Patent Document 1: Japanese Unexamined Patent Application Publication No. 10-151131        Patent Document 2: Japanese Unexamined Patent Application Publication No. 2002-112998        